Increased risk

The study, by researchers at Huazhong University of Science and Technology in China, showed shift workers were 9% more likely to have type 2 diabetes.

But in men, the figure was 35%. And for people chopping and changing between day and night shifts, the risk increased by 42%.

The researchers said: "The result suggests that male shift workers should pay more attention to the prevention of of diabetes.

"Given the increasing prevalence of shift work worldwide and the heavy economic burden of diabetes, the results of our study provide practical and valuable clues for the prevention of diabetes."

Possible explanations include shift work disrupting sleeping and eating patterns. One idea is that eating late at night makes the body more prone to store the energy as fat, increasing the risk of obesity and in turn type 2 diabetes.

The increased risk in men could be down to changes in levels of male hormones, it has been suggested.

Also, because the studies are looking at only one snapshot in time it is impossible to say definitively that shift work causes diabetes as other factors could be at play.

The type of person more prone to type 2 diabetes may be more likely to become a shift worker.

One of the researchers, Prof Zuxun Lu, told the BBC: "Shift workers should be educated about diabetes symptoms in an effort to forestall or avert the earliest clinical manifestations of disease.

"Improved shift modifying strategies should be implemented into the company's management scheme to effectively protect shift worker from diabetes.

"Finally, the increased risk of diabetes apparent in rotating shift group and male shift workers, suggests that people who do shift work should pay more attention to the prevention of diabetes."

"They can do this by taking a type 2 diabetes risk assessment, either online or in their local pharmacy.

"The best way to reduce your risk of type 2 is to maintain a healthy weight through regular physical activity and by eating a healthy balanced diet."

Prof Nick Wareham, from the University of Cambridge, said any effect was moderate.

He added: "If it were shown that it is shift working itself that has a link to diabetes, then the key question would be to identify what interventions could be put in place to alleviate the risks in those who have to work shifts."